Metal working and liquid coolants therefor



United States Patent lVlETAL WORKING" AND LIQUIDRCOOLANTS THEREFOR:

Thomas H. Cafcas Chicago, Ill.,. assignor to Standard Oil Company, Chicago, Iil., a.corporation of Indiana No Drawing. Application March-30,1954, SerialzNor- 419 9.05

5' Claims. (Cl; 251-333).

Thisinvention relates. to metal working and morepar-v ticularly pertains to improved liquid coolants for usein metal, working operations.

In. metal. working operations liquid coolants. are em? ployed to prevent overheating of the work. piece and. the tool. The liquid coolant functions also to lubricate the contactingsurfaces of the tooland work piece. The various metalworking operations which employ liquid. coolantsare those such as cutting, turning, drilling, grind ing, and similar operations performed'on metals such as iron steel, copper; bronze, andth'e like. In the usual metal working operation, the tool" and. work piece are. washedwith the coolantwhiclr removes thev metal particles formed during the metalworking operation and. also cools thetookandgwork'piece; Provision is usually made torremovingat leastia part of the metal particles. by settling before-'recirculatingth'e coolant: If the metal particles are not substantiallymemoved from the coolant prior to. recirculation, the metal chips are recirculated to. the point of contact of the tool and workpieceandr seriously interfere in the metal working operation. in

before the latter is recirculated to the point of contact of the grinding wheel? with. the; metal-i work. piece, the pores and cavities of the grinding Wheel become filled with the grindings. This=condition is commonly called wheel-loading. In this condition the grinding wheel is less abrasive and has uneven projections on its-- surface; When grinding with such -a-wheel,- thefinished= work piece* may have a scouredsurface, chatter marks, andanonuniform. roughened finish; The grinding wheel which has its. surface loaded with metal g-rindings will' not grind theworkpieceas rapidlyas a fresh wheel since its .abrasiveness issreduced, andathe operatonmusttneces sarily work at a slower'rate: As-the grindii1g wheel-be comes loadedwith metal. grindings; it develops rgrooves: on its surface which require, the..wheelto be. dressed to-a: levelor uniformsurface- Becausedressing of thewheel removes useful abrasive. surface, the life of the "grinding,

wheel is greatly reduced. Inaddition; thedressing operationdecreases the, time: during,,which thegrinding wheel and its operatorare: available: for grindingroperations.

An object of'this invention. is. to provide. a liquid coolant useful in metal workingpperations andtwhich.

jects andadvantages willbet apparent in thecoursmoffthe detailed description of the invention.

it has been discovered,thatifwasmallamount ofian alkylene. diamine tetraacetic... acid,.,or.. the. ammonium 1 or alkali-metalsalt thereofisv added too-liquid coolant-such:

as the soluble-oil type. or the toll-free aqueous type-=whieh is then used in a metal working operation, the metal particles settle more rapidly in the coolant solution: It has also been discovered that these compounds impart rust-proofing properties to the coolant. The alkylene diamine derivative may be a butylene-, propylene-, methylene-, and is preferably an ethylene diamine tetraacetic acid or thearnmonium or alkali metal salt thereof. The alkali metalsalt, particularly the sodium salt, of ethylene diamine tetraacetic acid is preferred. The mono-, di-, tri-, or tetra-sodium salt may be employed. The. alkylene diamine tetraacetic acid or its ammonium or alkali metal salt, which shall hereinafter bereferredto as the settlingagent, may be added in an amount between about OLOS to 20%, preferably 0.1 to 10%, to aconcentrate of the coolant which may be of the soluble-oil type orthe oil-freeaqueous' type. The concentrate may then. be dilutedwith between about 5 to parts ofwater and'used inmetalbetween abouLOlOOl to 5%, preferably 0.01 to 0.5% of.

the metal. particie settling agent.

The settling agents of this invention are effective in coolants. such as the soluble oil type and the oil-free aqueous type. The. settling agent'may be added to the concentrated form or tothe diluted form of the coolant as' used inLthe'metal working operation. It is more conveniently added tothe concentrate-form. The solubleoil type' concentrate generally comprises base oil and anioil-in-water emulsifyingagent. It usually contains a'rust-proofingagent andoptionally itmay contain vary.- ing amounts ofdispersihgagents, bactericides and the like. Examples of conventional formulae-for soluble-oils to'wh'ich the settling'agent" may be added'in amounts of about 0.05 to 20% areillustratedin' Formulae A and B which follow. in" these. formulations and wherever a percentage, part, or portion is expressed in thespecification or claims, it is intended on. a weight basis which is based'upon' the total components listedtherein.

Formula A- Weight 'percent A general'formula for concentrates vof the oil-free aque ous-type coolaut is' set forth below'in' Formula C. The

settling agent may be added in an amount betweeniabout 0.05 to --20%" to the concentrate solution illustrated?" Formula- C Weight percent Rust-proofingagent S SO' Load'carryingagent 0*20 Dye 0-0.1 Water 50-95' The soluble oils of- Formulae A-and'-B"-and the-'oil-freeaq'ueouetype concentrate of Formula C may 'be' diluted withj toi lSOpartS of water and used in the-'diluteclform" as liquid coolants for metal working operations. Examples of other coolants to which the settling agent may be added are disclosed in U. S. P. 2,436,046 of N. E. Lemmon et al.; U. S. P. 2,231,214 of R. F. Nelson et al.; U. S. P. 2,252,385 of G. H. Orozco; and U. S. P. 2,289,536 of W. E. Bradley.

The soluble-oils of Formulae A and B contain varying amounts of a base oil. The base oil comprises a hydrocarbon oil such as petroleum or a synthetic hydrocarbon oil. The base oil should have a Saybolt viscosity of about 60 seconds or more at 100 F. and preferably has a Saybolt viscosity of about 75 to 150 seconds at 100 F. The soluble-oil of Formula A is the type most commonly used by metal working industries and it contains 45 to 95% of base oil, preferably between about 75 to 90%.

Suitable emulsifying agents which may be used in the soluble-oil compositions are oil-in-water emulsifiers such as the soaps of preferentially oil-soluble sulfonic acids, soaps of naphthenic acids, soaps of rosin acids and other emulsifying agents such as the non-ionic emulsifiers. Examples of suitable non-ionic emulsifiers are the ethylene oxide condensation products with sorbitan oleates, laurates, and the like. The soap of the preferentially oil-soluble sulfonic acid, naphthenic acid, rosin acid, or the like, is preferably an ammonium, amine, or alkali metal soap. For example, organic naphthenates such as diethanolamine and triethanolamine naphthenate may be used. The soaps of the preferentially oil-soluble sulfonic acids may be prepared by reacting a petroleum distillate with sulfuric acid and neutralizing the organic sulfonic acids thus produced with an appropriate alkaline solution such as an aqueous solution of sodium hydroxide. Either a single emulsifying agent or a mixture of two or three emulsifying agents may be employed in the soluble-oil. For example, the total emulsifying agent used may be comprised of 5 to 25% of sodium rosinate and 75 to 95% of a sodium sulfonate, and this latter mixture of emulsifying agents is preferred for use in the soluble-oil. In general, the total amount of emulsifying agents may comprise between about 2 to 30%, preferably about 5 to 20% of the soluble-oil.

Any of a Wide variety of effective rust-proofing agents may be employed in the soluble-oil. For example, the alkylolamines such as mono-, di-, and triethanolamine, propanolamine, butanolamine, and the like, the hydroxamic acid derivatives such as naphthene hydroxamic acid, the ammonium, amine, or alkali metal chromates, salts such as the ammonium, amine, or alkali metal salts of nitrous acids, e. g. sodium nitrite, and the like, may be used. The emulsifying agents generally have some degree of rust-proofing ability and thus serve a double function in the soluble-oil coolant. The soaps of preferentially oil-soluble sulfonic acids are notable examples of such a dual functioning agent. The rust-proofing agent is usually employed in the soluble-oil in amount between about 0.1 to 5%, preferably about 0.25 to 1%. It has also been noted that if the soluble-oil or aqueous-type coolant is somewhat alkaline, its rust-proofing ability is somewhat improved.

Suitable dispersing or coupling agents may be contained in the soluble-oil composition to improve the clarity and stability of the soluble-oil. The dispersing agent ordinarily may comprise an approximately equal mixture of water and an alcohol such as a monohydric alcohol, polyhydric alcohol, or alcohol ether. Examples of these alcohols include ethanol, propanol, isopropanol, butanol, diethylene glycol, ethylene glycol monobutyl ether, and the like. It is not always essential to employ the dispersing agent, but it is sometimes desirable to do so particularly to improve the stability of the emulsion of oil when dispersed in widely varying amounts of water. When it is employed in the soluble-oil it is contained therein in a concentration between about 0.5 to 5.0%, preferably between about 1 to 2% by weight. If desired, bactericides such as 0.1 to 1%, ordinarily about 0.25%

of a chlorinated phenol such as tetrachlorophenol, trichlorophenol, or the like may be added to the soluble-oil. Load carrying agents such as sulfurized mineral, animal, or vegetable oil, e. g. sulfurized lard oil, may be added to the soluble-oil in an amount between about 0.1 to 20%, preferably about 5 to 12% by weight. I have discovered that thiourea functions as a load carrying agent in coolants of the type described herein, and that it is particularly effective in the oil-free aqueous-type coolants. This latter discovery constitutes the subject matter of my application S. N. 419,906 filed on even date herewith.

The soluble-oil containing the settling agent may be prepared by adding emulsifying agent to the base oil in the desired proportion and maintaining the temperature of the mixture at about 75 to 120 F., preferably about to 110 F., and then adding the dispersing agent, rustproofing agent, bactericide, and load carrying agent in the amount desired to the mixture. The settling agent is then added, in the desired water if any, to the soluble-oil.

The following soluble-oil compositions are illustrations of this invention and should not be interpreted as limiting the scope thereof:

1 Non-ionic emulsifying agent comprising reaction product of ethylene oxide with sorbltan trioleate.

Example III Weight percent Sodium sulfonate 4.6 Sodium chromate 4.6 Tween 20 3.7 Petroleum oil S. S. U. at 100 F.) 4.5 Water 78.6 Ethylene diamine tetraacetic acid 4.0

Non-ionic emulsifier comprising the reaction product of ethylene oxide with sorblran monolaurate.

The concentrates of the oil-free aqueous-type coolants shown in Formula C are comprised essentially of water containing a rust-proofing agent soluble therein. Examples of highly water-soluble rust-proofing agents are ammonium or alkali metal nitrites or chromates, or the alkylolamines such as mono-, di-, or triethanolamine, morpholine, and the like. Mixtures of such rust-proofing agents may be employed rather than a single agent. An approximately equal mixture of an alkali metal nitrite, e. g. NaNOz, with an alkylolamine such as ethanolamine is preferred for use in this oil-free aqueous-type coolant. Bactericides, dyes, load carrying agents particularly thiourea, and other agents may be present in the concentrated or dilute form of the aqueous-type coolant.

The oil-free aqueous-type coolant may be a concentrate solution in water or it may be a mixture of the various agents containing no added water. If the concentrate is prepared on a water-free basis, a mixture in any proportion of the rust-proofing agent and the metal particle settling agent may be used. Preferably, the ratio of rustproofing agent to settling agent may vary between about 1:3 to 50:1, usually about 5:1. When the concentrate tween about 5 to 50%, preferably about to 30%, of

the rust-proofing agent which preferably consists of about equal portions of alkali metal nitrite and ethanolamine, between about 0.05 to 20% and preferably 0.05 to 10% of the settling agent, with water comprising the remainder. The sodium salt of ethylene diamine tetraacetic acid is the preferred settling agent for use in the aqueous-type coolant. The concentrate solution can be made by adding the components in the desired amounts in any sequence to water which is maintained at a temperature of 60 to 120 F., preferably about 100 F., and stirring until solution is complete.

Examples of concentrates of the oil-free aqueous-type coolants are given below:

Example IV Weight percent Sodium nitrite 10 Ethanolamine 10 Thiourea 10 Tetra-sodium salt of ethylene diamine tetraacetic acid- 4 The effectiveness of the metal particle settling agents of this invention was demonstrated in a grinding operation designed to give a measurable indication of the rate at which the grindings settle. The test comprised grinding a cast iron work piece and circulating coolant in the usual manner by washing the wheel and work piece, allowing the coolant to drain into a sump containing the coolant and grindings, and then recirculating the coolant to wash and cool the grinding wheel and work piece. The sump was divided into two sections by a vertical bafile which had a weir along its upper horizontal edge for the flow of coolant from compartment 1, which held coolant as it descended from the work piece, into compartment 2 wherein the circulating pump picked up coolant and recirculated it to the work piece and tool. Because coolant is recirculated at a rapid rate, the settling rate of the metal particles is usually not sufficient to counteract the circulating direction and rate of travel of the coolant, and consequently, the metal particles tend to be somewhat below but near the surface of the liquid coolant in the sump as it is being circulated. The metal particles will thus normally pass from compartment 1 into compartment 2 and from there they are frequently circulated along with the coolant to the work piece and grinding Wheel with attendant damage thereto. In the experiments performed, the cast iron work piece was ground for approximately two hours with recirculation of the coolant, after which time the grinding was discontinued. The coolant was decanted from the sump and the weight of the metal particles in each compartment was estimated. The weight percentage of metal grindings and other particles in each compartment gives an indication as to the effectiveness of the coolant solution for settling metal particles, viz. the higher the percentage of metal particles in compartment 1, the more rapid is the rate of settling of the metal particles. The effectiveness of the settling agent in the soluble-oil type and the aqueous-type coolants is shown by the data set forth in the following table:

TABLE 1 Metal Particle Wt. Settling percent Coolant Settling Agent in Wt. per- Wt. per- Coolant cent in cent in Gompart- Compartment 1 merit-2 Example I -w ./.o settling agent None 50 50 Example I 1 0.07 10 Example IV w./o. settling agent None 50 50 Example IV 1 0. 06 90 10 1 The soluble-oil composition of Example I which is diluted with 7 parts of water to form the coolant used.

3 The concentrate solution oi Example IV which is diluted with 66 parts of water to form the coolant used.

It will be noted from the data in the above table that the coolants which contained the ethylene diamine tetraacetic acid compound were much more effective for settling the metal particles than the same coolant composition which did not contain the settling agent. Visual inspections of the work piece, the grinding wheel, and apparatus were made. It was noted that when the settling agent was employed in the coolant the grinding wheel had a smooth uniform surface free of loading, the grinding apparatus was free of rust, and the work piece had a smooth rust-free surface devoid of scouring.

Other liquid coolant compositions to which the settling agent is added display a similar, although not necessarily equivalent, improvement in the rate of settling of the metal particles within the coolant solution.

It is apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore, it is not to be limited except as indicated in the appended claims.

I claim:

1. An emulsifiable soluble-oil comprising between about 45 to of a hydrocarbon oil, between about 2 to 30% of an alkali metal soap of a preferentially oilsoluble sulfonic acid, and between about 0.05 to 10% of an alkali metal salt of ethylene diamine tetraacetic acid.

2. A liquid coolant which comprises from about 5 to parts of water per part of an emulsifiable solubleoil comprising between about 45 to 95% of hydrocarbon oil, between about 2 to 30% of an alkali metal soap of a preferentially oil-soluble sulfonic acid, and between about 0.05 to 10% of an alkali metal salt of ethylene diamine tetraacetic acid.

3. An emulsifiable soluble oil comprising between about 45 to 95% of a hydrocarbon oil, between about 2 to 30% of an oil-in-water emulsifying agent, and between about 0.05 to 20% of at least one alkylene diamine compound having the general formula CH2COOX CHuCOOX wherein n is an integer of from 1 to 4, and X is a monovalent radical selected from the class consisting of hydrogen, alkali metals, and ammonium.

4. The composition of claim 3 wherein the alkylene diamine compound is an alkali metal salt of ethylene diamine tetra-acetic acid.

5. The method of minimizing the quantity of suspended metal particles in a liquid coolant which is recirculated onto the tool and work piece during a metal working operation, which method comprises employing a coolant comprising about 5 to 150 parts of water per part of an emulsifiable oil comprising between about 45 to 95% of hydrocarbon oil, between about 2 to 30% of an oil-in-water emulsifying agent, and between monovalent radical selected from the class consisting of 7 about 0.05 to 20% of at least one alkylene diamine comhydrogen, alkali metals, and ammonium.

pound having the general formula References Cited in the file of this patent XOOC-HaC cmcoox N(CH=)..N 5 UNITED STATES PATENTS xooc-mo omcoox 2,252,385 Orozco Aug. 12, 1941 2,552,913 Waugh May 15, 1951 wherein n is an integer or from 1 to 4, and X is 9. 2,631,978 Bersworth Mar. 17, 1953 

5 . THE METHOD OF MINIMIZING THE QUANTITY OF SUSPENDED METAL PARTICLES IN A LIQUID COOLANT WHICH IS RECIRCULATED ONTO THE TOOL AND WORK PIECE DURING A METAL WORKING OPERATION, WHICH METHOD COMPRISES EMPLOYING A COOLANT COMPRISING ABOUT 5 TO 150 PARTS OF WATER PER PART OF AN EMULSIFIABLE OIL COMPRISING BETWEEN ABOUT 45 TO 95% OF HYDROCARBON OIL, BETWEEN ABOUT 2 TO 30% OF AN OIL-IN -WATER EMULSIFYING AGENT, AND BETWEEN ABOUT 0.05 TO 20% OF AT LEAST ONE ALKYLENE DIAMINE COMPOUND HAVING THE GENERAL FORMULA 